Beijing - Some call it a weapon in the hands of a righteous army, forged so that wrongdoers might be smitten. Others say it simply allows a mob of vigilantes to publicly vilify and humiliate anyone they choose to pick on through grotesque invasions of privacy.

Either way, the peculiarly Chinese Internet phenomenon known as the "human flesh search engine," a citizen-driven, blog-based hunt for alleged undesirables, claimed a fresh victim this month when a mid-ranking government official lost his job.

Accused of accosting a young girl, Lin Jiaxiang found his name, address, phone number, and workplace plastered all over Chinese cyberspace for 250 million Internet users to see, and his alleged crime the subject of hundreds of insulting blog postings.

Mr. Lin might be thought to have gotten his just deserts, especially since the police refused to prosecute him because he'd been drunk. Grace Wang, however, a Chinese student at Duke University, was outraged when netizens back home, offended by her efforts to mediate a campus dispute between pro-Tibetan and Chinese students last March, tracked down her parents' address and emptied a bucket of feces by their front door.

Once the actions of Ms. Wang and Lin had attracted attention in Internet chat rooms, both were quickly identified by people who recognized the photos of them posted on the Web.

It was not long before others who knew them had created an ad hoc human flesh search engine, and began posting many other personal details about the two.

With more Internet users than anywhere else in the world, there is no shortage of amateur detectives ready to join the hunt. And with chat rooms the only public space where Chinese citizens can express themselves anonymously and with any real freedom, they have become forums for strong opinions on many issues.

"It is a tradition in China," says Yu Hai, a sociologist at Shanghai's Fudan University. "People here like to moralize. And since traditional media are government mouthpieces, the Internet has become a very convenient channel for ordinary people to vent their feelings."

They can do so pretty much however they like, not only because they can disguise their identities, but also because there is no privacy law in China yet. "There is no practicable, feasible, and concrete legal instrument" to regulate Internet use, says Li Xu, deputy head of Tsinghua University's Institute for Internet Behavior.

One man who found himself the quarry of a human flesh search, Wang Fei, is testing the law by bringing China's first suit against websites that he says carried defamatory statements about him.

Mr. Wang drew the ire of fellow Internauts after his wife committed suicide last year. Her diary, posted posthumously by her sister, voiced suspicions that Wang had an affair with a colleague. The blogosphere blamed Wang for his wife's death, and turned on him with a vengeance.

"You will fall into the endless darkness and abyss of misery hated by billions" read one post, labeling Wang a "beast" and "scum."

The virtual insults spilled over into real life. Someone painted "blood for blood" on Wang's front door, his lawyer said. He and his relatives were bombarded with furious telephone calls, and he was fired from his job at an advertising agency, along with his alleged mistress.

"Those websites published insulting, defamatory, and untrue information about Wang that damaged his reputation ... and violated his privacy," argues his lawyer, Zhang Yanfeng. "He is suing them for damages, for mental distress, and lost earnings."

The case has already taken nine months and will probably not come to judgment until next spring, says Mr. Zhang, because of "a great many disagreements" among the judges and the expert witnesses.

Among the issues the court must resolve, in the absence of any clear legislation, is whether information such as a cellphone number, an ID card number, or an address can be said to be private. The judges must also consider how far website managers are responsible and legally liable for posts on their sites, and weigh the competing interests of free speech and privacy protection.

A poll published earlier this year in the China Youth Daily found that nearly 80 percent of respondents thought that human-flesh search engines should be regulated, and 65 percent thought they invaded people's privacy.

The dilemma, says Dr. Li, is that "allowing arbitrary speech with no regulation ... violates privacy rights. But if you over-regulate citizens' ability to express themselves, the Internet will lose its very nature and its attraction."

Drawing too heavy a cloak around personal privacy, moreover, would protect abusive officials from the public pillorying they deserve, argues Liu Deliang, head of the Asia-Pacific Institute for Cyberlaw Studies.

"Ordinary people have no enforceable right to supervise government officials' behavior or to control the corruption they see everywhere," he says. "So they use the Internet to do that."

"Human-flesh searches are a neutral technology that can be used for good or ill," says Dr. Liu. "But they must strike a balance between public and private interests."